When warmer summers eat at the permafrost, pecking beaks hardly make the situation better.

Svalbard is greening. As the air gets milder, giving the tundra more to offer, birds are tempted to migrate farther north. Flocks of geese feast in the valleys, with table manners that both enhance and work against the greening.

"The tundra looks as if a lot of people have been hiking there with poles," says Lise Øvreås, describing valley floors perforated by goose beaks.

The professor at the Department of Biological Sciences at the University of Bergen, and the Bjerknes Centre coordinates a research project on birds and permafrost.

The aim is to find out how grazing geese influence the thawing ground as well as its microbes and plants.

"Moss," she says. "Moss is important. Moss keeps the soil cool, humid and stable."

When large flocks of geese search for food, they chop up the insulating layer of moss that shields the ground from sun and mild summer air.
Warmer weather is obviously the most important factor behind the thawing of permafrost. But what happens when thousands of beaks dig into the moss?

How much of a menace can a goose be?

Pretended to be birds

In the valleys around Longyearbyen professor Øvreås and colleagues from the University of Bergen and The University Centre in Svalbard (UNIS) have marked out patches of approximately one square meter.

Each patch represents specific characteristics of the tundra, with or without species such as Dryas octopetala and Salix polaris, with or without ice in winter and not least important: with or without pecking beaks.

"We pretended to be geese and rubbed and picked at the moss."

Lise Øvreås forms a goose beak with her hand and chops in the air to illustrate scientists and birds.
Thawing permafrost is associated with collapsed houses and sinkholes. But the thaw also has consequences on smaller scales, for plants and microbes in the soil. As ice no longer blocks the access, bacteria and other microbes penetrate farther down.
Microbes are also influenced in other ways. Geese do more than merely expose frozen ground.

Goose shit greens the ground

"They poop like crazy."

In recent years Lise Øvreås has seen the tundra becoming greener in the geese's grazing fields. Not only do the birds poop, they poop in their own food tray, with great success. They fertilize the soil with nitrogen, which Svalbard plants otherwise have limited access to.

To find out how much this additional supply of nitrogen means, the researchers gathered a kilogram of goose shit, which they dried and distributed in their test field.

This fertilization would have been of limited use without microbes living underground. Plants cannot take up all forms of nitrogen from the soil, and certainly not from the air. Their uptake depends on interaction with bacteria.

Goose shit contains ammonia, from which plants – as opposed to nitrogen gas in the air – can take up nitrogen directly. But the uptake accelerates if microbes first convert ammonia into nitrate.

Beneficial cohabitation

The roots of pea and raspberry plants have tubers containing rhizobia – soil bacteria that fix nitrogen from the air and pass it on to the plant.
On the mainland, with plenty of plants and trees, this symbiosis between plants and rhizobia is important. Though sparse, the vegetation in Svalbard has been shown to be richer in rhizobia than previously assumed.

"Cyanobacteria," says Lise Øvreås. "Large, green blobs of rubbery flakes you can pick up. We find a lot of these in Svalbard, and they also fix nitrogen."

The field microscope she always carries, is sufficient to see the glass-like cells the flakes consist of, cells that absorb nitrogen from the air and make the substance available to plants.

Plants may get less nitrogen

Traditionally, cyanobacteria have been considered important for providing tundra plants with nitrogen. The question is whether this will continue to be the case.

"Recent research suggests that biological nitrogen fixation has been optimized for low temperatures, so that the climate change now seen in the Arctic, may lead to a decrease," says Lise Øvreås.

After two years of measurements, the researchers have packed up their equipment. Now, the analysis of all the data they have collected remains, of nitrogen, carbon, temperature, humidity, ice and not least:

"Moss," says Lise Øvreås. "Gases have been trapped in the permafrost for thousands of years. Now they are being released."

The geese have flown south but will soon return.

FACTS: Project TERRA

feedbacks (TERRA)
Partners:

• University of Bergen
• The University Centre in Svalbard (UNIS)
• Norwegian University of Science and Technology (NTNU)
• Norwegian University of Life Sciences (NMBU)
• Swedish University of Agricultural Sciences (SLU)
• University of Copenhagen (KU)
• Lawrence Berkeley National Laboratory

Funding: The Research Council of Norway
Project coordinator: Lise Øvreås

Facts: Lise Øvreås

• Professor of geomicrobiology at the Department of Biological Sciences at the UiB, and the Bjerknes Centre.
• President of The Norwegian Academy of Science and Letters (DNVA), 2022–2024.
• Vice-President of European Academies Science Advisory Council (EASAC), 2024–2026.
• Professor II at UNIS.